1. Field of the Invention
This invention relates generally to a system and method for waking up a controller during a refueling process of a hydrogen gas storage tank and, more particularly, to a system and method for waking up a controller during a refueling process of hydrogen gas storage tank by monitoring the temperature of the storage tank and the temperature of the hydrogen gas at the refill port when the controller has previously been shut down to conserve battery power.
2. Discussion of the Related Art
Hydrogen is a very attractive fuel because it is clean and can be used to efficiently produce electricity in a fuel cell. The automotive industry expends significant resources in the development of hydrogen fuel cell systems as a source of power for vehicles. Such vehicles would be more efficient and generate fewer emissions than today's vehicles employing internal combustion engines.
Typically, hydrogen gas is stored in one or more compressed gas tanks under high pressure on the vehicle to provide the hydrogen gas necessary for the fuel cell system. The pressure in the tank can be upwards of 700 bar. In one known tank design, the tank includes an inner plastic liner that provides a gas tight seal for the hydrogen gas, and an outer carbon fiber composite layer that provides the structural integrity of the tank. Because hydrogen gas is a very light and diffusive gas, the inner liner and the tank connector components must be carefully engineered in order to prevent leaks. The hydrogen gas is removed from the tank through a pipe. At least one pressure regulator is typically provided that reduces the pressure of the hydrogen gas within the tank to a pressure suitable for the fuel cell system.
The hydrogen gas storage tanks on fuel cell vehicle are refueled at a suitable refueling station where the appropriate receptacles, piping, valves, etc. are provided to couple the tanks to a larger source of hydrogen gas. Often, these types of refueling stations are able to refill the hydrogen gas storage tanks on the vehicle very quickly by providing a fast flow of hydrogen gas at a significantly higher pressure. If the hydrogen gas storage tank is near empty and at low pressure, the fast flowing hydrogen gas entering the tank will quickly expand, causing it to significantly and quickly increase in temperature. Typically, the temperature within the tank will not significantly increase if there is a high enough pressure within the tank during the refueling process. Because the inner liner of the tank providing the gas tight seal is a polymer, high temperatures within the tank have a degrading effect on the liner, which could ultimately lead to loss of seal integrity over time and a number of refueling events. Because of this concern, it is known in the art to provide a temperature sensor on the tank that monitors the temperature of the hydrogen gas during a refueling event, where the temperatures are recorded during refueling over time. An algorithm is provided to determine the durable life of the liner based on how often the temperature precedes a predetermined temperature and for how long.
Some refueling stations are SAE approved and receive communications signals from the vehicle during the refueling process. For SAE approved refueling stations, the various temperature and pressure signals are observed by the vehicle. Other refueling stations may not be SAE approved, where the vehicle independently needs to monitor the temperature of the tank during the refueling process using the temperature sensor.
In one known fuel cell system design, the refueling door or flap that is opened during the refueling process to expose the refueling receptacle that is connected to the refueling station has a switch that is closed when the flap is open to provide a signal to a vehicle controller that a refueling event is about to begin. If the vehicle is off, the controller will wake-up when the switch is closed in anticipation that refueling will soon commence to record the temperature signals from the temperature sensor when monitoring the flow of the hydrogen gas to the tank. There is also an observation of the tank pressure and the hydrogen concentration. In some situations, the vehicle driver may open the refueling flap, but not immediately begin the refueling process. Because the battery state-of-charge of the low volt battery on the vehicle has limited charge and is not recharged when the vehicle is off, algorithms are provided to reduce or control the power draw from the battery. In one design, the controller that monitors the flap switch will only stay woken up for a certain time after the switch is closed, and if the refueling process is not initiated during that time, will shut down to save battery power even though the flap switch is closed. If the driver then performs the refueling process after the controller has shut down, the controller will not be able to monitor the temperature and pressure during that refueling event, which could have consequences for determining the usable life of the tank.